Physicians have used elastic ligating bands to treat lesions, including internal hemorrhoids and mucositis and for performing mechanical hemostasis. The object of such ligation is to position a ligating band, which is usually elastic, over the targeted lesion or blood vessel section by first stretching the band beyond its undeformed diameter and then drawing the tissue to be ligated within the band. Thereafter the band is released so that it contracts, applying inward pressure on the section of tissue caught within the band. The effect of the inward pressure applied by the band is to stop all circulation through the targeted tissue, thereby causing the tissue to die. The body then sloughs off the dead tissue or the dead tissue may be aspirated into an endoscope or a similar device.
U.S. Pat. No. 5,398,844 to Zaslavsky et al. (“the Zaslavsky patent”), which is incorporated herein by reference, describes a ligating band dispensing device including a substantially cylindrical support surface over which elastic ligating bands are stretched. The cylindrical support surface is typically attached to the distal end of an endoscope which is advanced into the body to a target area. A user then applies suction through the endoscope to draw the tissue to be ligated into the cylindrical support surface and releases a ligating band to contract around the tissue.
Previous ligating band dispensers allowed a user to dispense only a single ligating band at a time. That is, after a single ligating band was dispensed, if a user wanted to ligate another portion of tissue, the user would remove the device from the patient's body, load a new ligating band on the device and reinsert the device to the desired area within the patient's body. The device of the Zaslavsky patent, allows a user to place several ligating bands at desired locations without removing the device from the patient's body to reload ligating bands. However, as the number of ligating bands included on the distal end of these devices has been increased, the field of vision from the endoscopes to which these devices are normally coupled has been correspondingly decreased.
More specifically, as shown in FIGS. 1 and 2 a known support surface 2 around which several elastic ligating bands 4 are received is mounted on the distal end of an endoscope 6. This support surface 2 is preferably formed of a rigid material, for example polycarbonate. The rigidity of this support surface 2 is necessary to maintain the size of the distal opening of the support surface 2 as the support surface 2 is subjected to compressive forces from the ligating bands 4 and from vacuum pressure used to draw tissue into a tissue receiving space 18 formed axially through the support surface 30. A proximal end of the support surface 2 is coupled to an elastic ring 8 formed of, for example, silicone. The elastic ring 8 grips the distal end of the endoscope 6 to frictionally couple the support surface 2 to the endoscope 6. A shoulder 10 formed at the juncture between the support surface 2 and the ring 8 maintains a predetermined separation between the distal-most surface 12 of the endoscope 6 and the distal end 14 of the support surface 2 to provide a space 18 within which the tissue to be ligated may be received. The space 18 is often substantially conical with a minimum diameter at a proximal end thereof of, for example, 0.375 inches and a maximum diameter at the distal end of the support surface of 0.5 inches. As the endoscope 6 is received only within the elastic ring 8 and does not extend into the rigid support surface 2, this support surface 2 may be coupled to endoscopes 6 of various diameters with no modification.
FIGS. 3 and 4 show cross-sectional views of other known support surfaces 2′ and 2″, each also being adapted to receive an endoscope so that the distal end 12 of the endoscope 6 abuts a proximal end surface 7 of the support surface 30. The distal end 12 of the endoscope 6 is received within the ring 8 but does not extend into the support surface 30. The space 18 within the support surface 2, which is of substantially uniform diameter throughout, is reserved only for receiving the tissue to be ligated. This is true for both the 8 ligating band receiving supporting surface 2′ and the 5 ligating band receiving support surface 2″.
Even if the support surface 2 is made of transparent material, the breadth of the visual field of an optical device 16 (shown by the dotted lines in FIG. 2) included in the endoscope 6 is limited by the extent to which the ligating bands 4 extend distally of the distal end 12 of the endoscope 6. And, as the number of ligating bands 4 is increased, the distal extension of the ligating bands 4 is also increased, resulting in a corresponding decrease in the extent of the visual field.